Optical rangefinding is generally accomplished by utilizing optical split imaging techniques. The target is viewed from two different locations and the images are superimposed. In such systems the angle of reflection required to achieve optical coincidence of the images is a function of range. Thus, if the operator adjusts the angle to achieve coincidence the adjustment can be calibrated to indicate range.
One disadvantage of such optical rangefinders is that the range accuracy is a function of mechanical and optical tolerances. Such systems become very costly if designed to measure range accurately, particularly at relatively large distances as is typical in shipboard applications. Another disadvantage is that optical rangefinders are difficult to incorporate in submarine periscopes because of the distance and optical couplings necessary between the viewing locations (above the water surface) and the superimposed images (inside the submarine).
An object of this invention is to provide a video rangefinding system capable of detecting range from a single view of the target, using a standard TV video input.
Another object of the invention is to provide a split image video rangefinder wherein the split images are created electronically rather than optically.
Still another object is to provide a video rangefinding system which is generally insensitive to the relative movement between the target and the viewing position such as is common in shipboard applications.